From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f169.google.com (mail-pf0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id 981B86B0254 for ; Mon, 7 Mar 2016 20:56:17 -0500 (EST) Received: by mail-pf0-f169.google.com with SMTP id 124so1301046pfg.0 for ; Mon, 07 Mar 2016 17:56:17 -0800 (PST) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [58.251.152.64]) by mx.google.com with ESMTPS id q5si915999pap.42.2016.03.07.17.55.00 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 07 Mar 2016 17:56:16 -0800 (PST) Message-ID: <56DE2DE8.6070509@huawei.com> Date: Tue, 8 Mar 2016 09:42:00 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: Suspicious error for CMA stress test References: <56D6F008.1050600@huawei.com> <56D79284.3030009@redhat.com> <56D832BD.5080305@huawei.com> <20160304020232.GA12036@js1304-P5Q-DELUXE> <56D91E18.1020807@huawei.com> In-Reply-To: <56D91E18.1020807@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hanjun Guo , Joonsoo Kim Cc: Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Sasha Levin , Laura Abbott , Catalin Marinas , Will Deacon , Arnd Bergmann , "thunder.leizhen@huawei.com" , dingtinahong , chenjie6@huawei.com, "linux-mm@kvack.org" On 2016/3/4 13:33, Hanjun Guo wrote: > Hi Joonsoo, > > On 2016/3/4 10:02, Joonsoo Kim wrote: >> On Thu, Mar 03, 2016 at 08:49:01PM +0800, Hanjun Guo wrote: >>> On 2016/3/3 15:42, Joonsoo Kim wrote: >>>> 2016-03-03 10:25 GMT+09:00 Laura Abbott : >>>>> (cc -mm and Joonsoo Kim) >>>>> >>>>> >>>>> On 03/02/2016 05:52 AM, Hanjun Guo wrote: >>>>>> Hi, >>>>>> >>>>>> I came across a suspicious error for CMA stress test: >>>>>> >>>>>> Before the test, I got: >>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>> CmaTotal: 204800 kB >>>>>> CmaFree: 195044 kB >>>>>> >>>>>> >>>>>> After running the test: >>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>> CmaTotal: 204800 kB >>>>>> CmaFree: 6602584 kB >>>>>> >>>>>> So the freed CMA memory is more than total.. >>>>>> >>>>>> Also the the MemFree is more than mem total: >>>>>> >>>>>> -bash-4.3# cat /proc/meminfo >>>>>> MemTotal: 16342016 kB >>>>>> MemFree: 22367268 kB >>>>>> MemAvailable: 22370528 kB >>> [...] >>>>> I played with this a bit and can see the same problem. The sanity >>>>> check of CmaFree < CmaTotal generally triggers in >>>>> __move_zone_freepage_state in unset_migratetype_isolate. >>>>> This also seems to be present as far back as v4.0 which was the >>>>> first version to have the updated accounting from Joonsoo. >>>>> Were there known limitations with the new freepage accounting, >>>>> Joonsoo? >>>> I don't know. I also played with this and looks like there is >>>> accounting problem, however, for my case, number of free page is slightly less >>>> than total. I will take a look. >>>> >>>> Hanjun, could you tell me your malloc_size? I tested with 1 and it doesn't >>>> look like your case. >>> I tested with malloc_size with 2M, and it grows much bigger than 1M, also I >>> did some other test: >> Thanks! Now, I can re-generate erronous situation you mentioned. >> >>> - run with single thread with 100000 times, everything is fine. >>> >>> - I hack the cam_alloc() and free as below [1] to see if it's lock issue, with >>> the same test with 100 multi-thread, then I got: >> [1] would not be sufficient to close this race. >> >> Try following things [A]. And, for more accurate test, I changed code a bit more >> to prevent kernel page allocation from cma area [B]. This will prevent kernel >> page allocation from cma area completely so we can focus cma_alloc/release race. >> >> Although, this is not correct fix, it could help that we can guess >> where the problem is. >> >> Thanks. >> >> [A] > > I tested this solution [A], it can fix the problem, as you are posting a new patch, I will > test that one and leave [B] alone :) > Hi Joonsoo, How does this problem happen? Why the count is larger than total? Patch A prevent the cma page free to pcp, right? ... - if (unlikely(is_migrate_isolate(migratetype))) { + if (is_migrate_cma(migratetype) || + unlikely(is_migrate_isolate(migratetype))) { ... Thanks, Xishi Qiu > Thanks > Hanjun > > > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org